Upgrading of spent butane isomerization catalyst to pentane isomerization catalyst

ABSTRACT

A fluoride-containing platinum on alumina support isomerization catalyst useful for the isomerization of pentane to isopentane can be prepared by a several step treatment of substantially deactivated chloride-containing platinum on alumina support isomerization catalyst. The conversion steps include washing the chloride-containing catalyst to remove substantially all chloride ions, fluorinating the washed material with an aqueous florinating agent, then drying the fluorinated catalyst. Isomerization process employing the catalyst thus prepared is also provided.

This invention relates to isomerization processes and catalyststherefore. In one aspect, this invention relates to the rejuvenation ofspent isomerization catalysts. In another aspect, this invention relatesto the conversion of catalysts useful for the isomerization of C₄hydrocarbons to catalysts useful for the isomerization of C₅hydrocarbons.

BACKGROUND

Platinum on alumina catalysts are useful for the isomerization ofsaturated hydrocarbons. These catalysts are subject to deactivation as aresult of prolonged usage for a variety of reasons. For example, thePhysical state of the platinum can change under long term exposure toisomerization conditions. Further, contaminants such as sulfurcompounds, metals and water in the feed over an extended period of timetend to deactivate the catalyst. Moreover, carbonization of the catalystand/or loss of activating catalyst adjuvants can also cause loss ofcatalyst isomerization activity.

Typically, "spent" (i.e., substantially deactivated) catalysts areprocessed to extract, separate and recover the platinum valuestherefrom. The recovered platinum values are then used to prepare freshcatalyst. Such a regeneration process is, however, an expensiveoperation because of the number of steps involved, the amount ofreagents required, etc. A process to readily convert a substantiallydeactivated isomerization catalyst to a once again active isomerizationcatalyst would, therefore, be of great benefit to those practicing inthe field of hydrocarbon isomerizations.

OBJECTS OF THE INVENTION

An object of the present invention, therefore, is the production of anactive isomerization catalyst from a substantially deactivatedisomerization catalyst.

Another object of the present invention is the isomerization of pentanesusing regenerated butane isomerization catalyst.

These and other objects of the present invention will become apparentfrom further study of the disclosure and claims provided herein.

STATEMENT OF THE INVENTION

In accordance with the present invention, I have discovered that anactive pentane isomerization catalyst can be prepared from asubstantially deactivated butane isomerization catalyst by subjectingthe butane isomerization catalyst first to a washing step underconditions suitable to remove substantially all chloride ions from thebutane isomerization catalyst, then treating the washed catalyst with atleast one aqueous fluorinating agent under conditions suitable toprovide intimate contact between the alumina support and thefluorinating agent, and finally drying the product of the fluorinationstep under conditions suitable to produce a substantially water freefluoride containing platinum on alumina support isomerization catalyst.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, a process for converting achloride-containing platinum on alumina isomerization catalyst to afluoride-containing platinum on alumina support isomerization catalystis provided which comprises first washing the chloride-containingcatalyst with wash medium under conditions suitable to removesubstantially all chloride ions therefrom, then treating the washedcatalyst with at least one aqueous fluorinating agent under conditionssuitable to provide intimate contact between the catalyst and thefluorinating agent, and finally, drying the fluorinated product underconditions suitable to produce a substantially water-freefluoride-containing platinum on alumina support isomerization catalyst.

In accordance with another embodiment of the present invention, processfor the isomerization of pentane is provided which comprises contactinga normal-pentane feed under isomerization conditions with a catalystprepared by first washing a chloride-containing platinum on aluminasupport isomerization catalyst with wash medium under conditionssuitable to remove substantially all chloride ions therefrom, thentreating the washed product with at least one aqueous fluorinating agentunder conditions suitable to provide intimate contact between thecatalyst and the flourinating agent, and finally, drying the fluorinatedproduct under conditions suitable to produce a substantially water-freefluoride-containing platinum on alumina support isomerization catalyst.

The catalyst employed in the practice of the present invention is aplatinum on alumina support isomerization catalyst which has beenpromoted with a chloride containing compound. The preferred catalyst isan aluminum chloride treated platinum on alumina catalyst which isuseful for butane isomerization. An especially preferred catalyst foruse in the practice of the present invention is a substantiallydeactivated aluminum chloride treated palladium on alumina catalystwhich has been employed for the isomerization of a butane-containingfeed.

The first step of the inventive conversion process comprises washing thechloride-containing platinum on alumina support isomerization catalystwith sufficient wash medium under conditions suitable to removesubstantially all chloride ions therefrom. Suitable wash media includewater as well as organic solvents in which the chloride ions to beremoved from the the catalyst are soluble and/or form a complex with thechloride ions such as for example alcohols, chlorinated hydrocarbons,esters, ethers, acids and the like, as well as mixtures of any two ormore thereof.

The volume of wash media employed is not critical and can readily bedetermined by those of skill in the art. Generally, at least enough washmedia should be employed to thoroughly contact the catalyst beingtreated. Preferably, sufficient quantity of wash media is employed toalso provide a displacement wash, thus aiding in the removal of thechloride ions. While in theory there is no upper limit as to the amountof wash media which can be employed, preferably less than about 10volumes of wash media per volume of catalyst will be employed tominimize disposal and/or recycle reconsiderations. Preferably, about 2to about 6 volumes of wash media per volume of catalyst to be treatedwill be employed.

The conditions employed for the washing step are not critical and can bereadily selected by those of skill in the art. While elevated as well asreduced temperatures can be employed, ambient conditions are preferredsince good results are obtained at ambient conditions and minimum energyrequirements are placed on the regeneration process when carried outunder such conditions.

Suitable fluorinating agents are water soluble fluorine-containingcompounds which are capable of reacting with the platinum on aluminasupport isomerization catalyst, many of which are known by those ofskill in the art. Exemplary compounds include HF, and quarternaryammonium fluoride compounds having the formula:

    (NR.sub.4)HF.sub.2

independently H or a carbon radical having 1-6 carbon atoms. HF ispresenily preferred because it is readily available, relativelyinexpensive, and is capable of essentially quantitative reaction withthe washed catalyst which is subjected to the flourinating treatment.

The amount of fluorinating agent employed for the fluorination step canvary widely. Sufficient fluorinating agent should be employed to providecatalyst having isomerization activity after the drying step, whilelarge amounts of fluorination agents are desirably avoided to minimizethe need to recycle and/or dispose of excess fluoride. Generally, anamount of fluorinating agent is employed to provide a finished catalystcontaining in the range of about 2-10 weight percent fluoride based onthe total weight of finished cata-yst. Preferably an amount offluorinating agent is employed to provide a finished catalyst havingabout 3-10 weight percent fluoride, based on the total weight offinished catalyst.

In accordance with the present invention contacting of the washedcatalyst with fluorinating agent is carried out in aqueous solution.Such contacting insures that uniform treatment of the washed catalyst isachieved. While the conditions of fluorinating agent-washed catalystcontacting are not critical, it is preferred for ease of operation thatcontacting be carried out at ambient conditions. Those of skill in theart recognize, of course, that contacting could be carried out at higheror lower temperatures as well as under reduced or elevated pressures.

The contacting between the fluorinating agent and washed catalyst shou-dbe maintained for a sufficient period of time prior to drying to allowreaction to occur between the fluorinating agent and the washedcatalyst. Generally, at least about 2 hours are required, with the upperlimit being set only by considerations of convenience.

Preferably, contact will be maintained for about 6-48 hours. The lengthof contacting period required will, of course, vary with the treatmentconditions employed, such that for example, longer times would beappropriate at lower temperatures while shorter times would be requiredat elevated temperatures.

Those of skill in the art recognize that care should be taken to scrubor otherwise suitably treat any off-gases produced in the contactingstep or in the subsequent drying step to prevent the release ofsubstantial quantities of fluorides from the process.

Drying of the fluorinated washed catalyst can be carried out by anysuitable technique known by those of skill in the art. For example, whenlarge volumes of treating solution are employed, excess liquid can beremoved by filtration, decantation or the like. The final, essentiallywater-free fluoride containing platinum on alumina support isomerizationcatalyst can then be prepared by drying at elevated temperatures, e.g.,90°-120° C. for a time in the range of about 0.5-6 hours.

In accordance with a particular embodiment of the present invention,process for the isomerization of pentane is provided employingfluoride-containing platinum on alumina support isomerization catalystprepared as described hereinabove. Thus, a pentane-containing feed istypically contacted with the substantially water-freefluoride-containing platinum on alumina support isomerization catalystin a plug flow fixed bed reactor. Suitable conditions for carrying outthe isomerization process of the present invention include a temperaturein the range of about 500°-800° F., pressure in the range of about500°-800° F., psig, a hydrogen to hydrocarbon feed ratio in the range ofabout 10:1-1:1, preferably about 2:1, and a liquid hourly space velocityin the range of about 0.2 to 6; preferably about 2.

A further understanding of the present invention and its advantages willbe provided by reference to the following nonlimiting examples.

EXAMPLE I

This example describes the regeneration of used butane isomerizationcatalyst (UOP I-4). Fifty grams of used Butamer catalyst was thoroughlywater washed to remove chloride, then oven dried at 110° C. Aftercooling to room temperature, the dried, washed catalyst was treated with39 g of 10% aqueous HF solution (about 7.8% F based on the weight ofcatalyst treated). The washed catalyst and HF solution were maintainedin contact at room temperature for about 24 hours, then oven dried at110° C. for about 4 hours. The dried, fluoride-treated catalyst was thencharged to a reactor tube for activation and isomerization studies.

EXAMPLE II

About 16.4 g of the fluorided catalyst prepared as described in ExampleI were loaded into a tubular reactor, bounded above and below by glassbeads. Catalyst was then reduced for about 48 hours at 750° F. andambient pressure under a trickle flow of hydrogen. Once the catalyst wasactivated, the reactor was pressured up to about 500 psig with hydrogen,then a mornal-pentane feed was begun. Reaction conditions, feed ratesand results are summarized in Table I.

                  TABLE I                                                         ______________________________________                                                                          n-C.sub.5                                   Sample                                                                              Temp.,  Press.  H.sub.2                                                                             n-C.sub.5                                                                           Conver-                                                                              i-C.sub.5                            #     °F.                                                                            psig    L/hr. mL/hr.                                                                              sion   Selectivity                          ______________________________________                                         1    700     500     38    56    37     98                                    2    730     500     38    56    52     95                                    3    760     500     38    57    61     95                                    4    760     500     38    59    63     91                                    5    760     500     14    27    64     93                                    6    760     500     61    91    55     93                                    7    760     500     40    63    69     97                                    8    760     500     73    107   49     97                                    9    760     250     73    107   49     97                                   10    760     250     56    82    55     97                                   11    760     250     38    60    60     95                                   12    760     250     19    26    66     95                                   13    760     125     13    29    63     95                                   14    760     125     36    55    55     95                                   15    760     125     56    81    32     97                                   16    760     125     74    112   25     94                                   17    760     500     32    61    41     95                                   18    760     500     32    29    50     95                                   19    760     500     39    61    56     97                                   ______________________________________                                    

The results presented in Table I demonstrate that rejuvenated butaneisomerization catalyst is active for isomerization of n-pentane (n-C₅)to isopentane (i-C₅) over a wide range of feed flow rates, reactionpressures and reaction temperature.

The examples have been provided merely to illustrate the practice of myinvention and should not be read so as to limit the scope of myinvention or the appended claims in any way. Reasonable variations andmodifications not departing from the essence and spirit of my invention,are contemplated to be within the scope of patent protection desired andsought.

I claim:
 1. A process for converting a chloride-containing platinum onalumina support isomerization catalyst to a fluoride-containing platinumon alumina support isomerization catalyst which comprises:(a) washingsaid chloride-containing catalyst with wash medium under conditionssuitable to remove substantially all chloride ions; (b) treating theproduct of (a) with at least one aqueous fluorinating agent underconditions suitable to provide intimate contact between said aluminasupport and said fluorinating agent; and (c) drying the product of (b)under conditions suitable to produce a substantially water-freefluoride-containing platinum on alumina support isomerization catalyst.2. A process in accordance with claim 1 wherein said chloride-containingisomerization catalyst is a butane isomerization catalyst.
 3. A processin accordance with claim 2 wherein said catalyst is a substantiallydeactivated butane isomerization catalyst.
 4. A process in accordancewith claim 1 wherein said wash medium is selected from the groupconsisting of:water, alcohols, chlorinated hydrocarbons, esters, ethers,organic acids,and mixtures of any two or more thereof.
 5. A process inaccordance with claim 1 wherein the volume of wash medium employedvaries within the range of about 2-10 volumes per volume of catalysttreated.
 6. A process in accordance with claim 1 wherein saidfluorinating agent is selected from the group consisting of:

    HF,

    (NR.sub.4)HF.sub.2,

wherein each R is independently H or a carbon radical having 1-6 carbonatoms, and mixtures of any two or more thereof.
 7. A process inaccordance with claim 1 wherein the amount of fluorinating agentemployed is sufficient to produce a finished catalyst having 2-10 wt %fluoride, based on the total weight of finished catalyst.
 8. A processin accordance with claim 1 wherein said conditions suitable to provideintimate contact between said alumina support and said fluorinatingagent comprise a temperature in the range of 0°-150° C., for a time ofat least one hour.
 9. A process in accordance with claim 1 wherein saiddrying conditions comprise an air atmosphere at a temperature in therange of 90°-120° C. for a time in the range of 0.5-6 hours.